Facebook also owns Instagram, which has attracted its share of
controversy for publishing new terms of service that would allow
it to put ads on the mobile photo-sharing app.

We asked Rob Leathern, the CEO of Optimal, one of the companies
that Facebook has tapped as a "preferred marketing developer."
Optimal helps clients run campaigns on Facebook.

"The magnitude of Facebook's owned and operated/native mobile ad
opportunities in the near term is huge," Leathern said. "Given
their bandwidth, I think it is probably just a prioritization
decision. Optimizing ad units for performance is not a trivial
undertaking at their scale."